A rubber component can look sound and still fail when it is stretched in service. A seal may split, a hose cover may tear, or a moulded part may lose the strength needed to hold its shape. ISO 37:2017 gives manufacturers, laboratories, buyers, and inspectors a recognised way to measure how vulcanized and thermoplastic rubber behaves under tensile loading.
This page explains what ISO 37:2017 is, what the test covers, how TNV Inspection Division uses it as a reference standard for inspection, and how we review rubber products and test evidence against it. TNV is a UAF accredited inspection body operating under ISO/IEC 17020:2012, and checking products against defined standards is the work we do.
What Is ISO 37:2017?
ISO 37:2017 is the international standard titled Rubber, vulcanized or thermoplastic — Determination of tensile stress-strain properties. It specifies methods for measuring the behaviour of rubber when a prepared test piece is pulled in tension under controlled conditions.
The standard is used to determine properties such as tensile strength, elongation at break, tensile stress at a specified elongation, and related stress-strain values. It does not set one universal pass or fail limit for every rubber product. Instead, it defines the test method so that results can be compared with a product specification, drawing, contract, regulatory requirement, or customer acceptance criterion.
That distinction matters. ISO 37 tells a laboratory how the tensile properties are determined. The applicable product requirement tells the manufacturer or inspector what result is acceptable.
What Does ISO 37 Cover?
The standard covers the main elements needed to produce a controlled and repeatable tensile test, including:
- Test pieces — Standardized dumb-bell and ring test pieces prepared from vulcanized or thermoplastic rubber.
- Dimensions and measurement — Measurement of the test piece thickness or cross-section so tensile stress can be calculated correctly.
- Conditioning — Control of the test-piece condition before testing because temperature, time, and prior treatment can influence rubber behaviour.
- Tensile testing — Extension of the test piece in a suitable tensile-testing machine at the specified rate until the required value is reached or the specimen breaks.
- Measured properties — Determination of tensile strength, elongation at break, tensile stress at specified elongations, and other stated stress-strain characteristics.
- Expression of results — Calculation and reporting of results together with the test-piece type, test conditions, and any relevant deviations.
The method is suitable for many rubber compounds and finished-product samples, provided representative test pieces can be prepared. Where specimen geometry, product construction, or available material does not allow the normal procedure, the agreed inspection or product specification should define how testing will be handled.
How the ISO 37 Tensile Test Works
A prepared rubber test piece is placed in the grips of a tensile-testing machine. The machine separates the grips at a controlled rate while measuring the force and extension. The original cross-section and gauge dimensions are used to calculate the tensile properties.
As the specimen stretches, the test records how much stress is needed to reach a stated elongation and how far the material extends before it breaks. These values help describe the compound’s strength, flexibility, and consistency.
A valid result depends on more than the machine display. The specimen shape, cutting quality, thickness measurement, conditioning, grip alignment, rate of extension, and point of break can all affect the outcome. This is why ISO 37 is valuable as a reference standard: it keeps these variables under control so different batches and laboratories can be compared on the same basis.
How TNV Uses ISO 37 as the Inspection Reference Standard
Every inspection needs a benchmark. For tensile properties of vulcanized and thermoplastic rubber, ISO 37 provides that benchmark. As a UAF accredited inspection body under ISO/IEC 17020, TNV Inspection Division can use the standard as the defined technical criterion when tensile performance forms part of a product inspection, purchase specification, production-control requirement, or customer acceptance plan.
That is what an inspection body means by a reference standard. ISO 37 defines how the tensile property is measured. Our job is to verify, independently and on the evidence, that the correct material was sampled, the test method was properly applied, the equipment and records were suitable, and the reported result was compared with the agreed requirement.
The outcome is an inspection report, not a product certificate under ISO 37. The report records what was checked, the evidence reviewed, the results observed, and whether the material met the stated acceptance criteria within the agreed scope.
How We Inspect Rubber Products Against ISO 37
Our inspection follows the agreed scope and the parts of the test process that are relevant to the product. In practice, an ISO 37-related inspection by TNV may cover the following:
- Product and material identification. We confirm the grade, compound, batch, drawing, purchase order, and product specification linked to the test samples.
- Sampling and traceability. We witness or verify sample selection and make sure each specimen can be traced back to the relevant lot or production batch.
- Specimen preparation. We review the test-piece type, cutting or preparation method, dimensions, surface condition, and any visible defects.
- Conditioning and environment. We check available records for conditioning time, temperature, and other agreed test conditions.
- Testing equipment. We review the tensile machine identification, load and extension measurement status, calibration records, grips, and measurement devices.
- Test execution. Where included in scope, we witness the extension rate, specimen alignment, break behaviour, and recording of force and elongation.
- Results and acceptance. We review calculations and compare the reported tensile properties with the contract, drawing, specification, or customer limit.
Our inspectors use document review, sample identification, observation, witness of testing, and record checks as required. Findings are recorded with evidence, and unusual breaks, specimen slippage, preparation damage, or other limitations are noted rather than ignored.
The deliverable is a clear inspection report. It states what was inspected, the applicable standard and acceptance criteria, the results or records reviewed, and any nonconformities, deviations, or limitations found.
Our UAF Accreditation Explained
This is what separates a real inspection body from a general service provider, so it is worth a moment.
TNV Global Limited (TNV) is accredited by the United Accreditation Foundation (UAF) for inspection under ISO/IEC 17020:2012 — Conformity assessment — Requirements for bodies providing various types of inspection. We hold that accreditation now, and we keep it through regular surveillance and witnessed inspections.
Our accreditation demonstrates that inspection activities are managed through defined methods, competent personnel, impartial decision-making, controlled records, and reviewed reporting. It also requires the scope and boundaries of every assignment to be clear before work begins.
What Our Accreditation Means for You
In practice, it gives you an independent result supported by a controlled inspection process. The product, lot, sampling basis, test method, acceptance criteria, and inspection stage are agreed in advance. Our inspectors remain separate from the parties whose material they inspect, and our reports state the evidence and findings without changing the result to suit a commercial outcome.
For ISO 37 work, that means the conclusion can be traced back to identified specimens, observed or reviewed test conditions, measurement records, calculations, and the requirement against which the rubber was judged.
Why Does ISO 37 Matter for Your Business?
Tensile properties are among the most widely used indicators of rubber quality. They help show whether a compound has been mixed, cured, and processed consistently, and whether the material is likely to provide the strength and extensibility expected in service.
For a manufacturer, ISO 37 supports batch control, product development, process monitoring, and investigation of failures. For a buyer, it provides a recognised basis for acceptance. For an inspector, it turns a general claim such as ‘high-strength rubber’ into a result that can be traced to a defined method and compared with a stated limit.
An independent inspection against agreed tensile requirements can also reduce disputes. Both parties know which test method applies, which samples were used, and how the conclusion was reached.
Differences Between ISO 37 and Other Related Standards
Rubber performance is measured through several different test methods, and each answers a different question:
- ISO 37 — Determines tensile stress-strain properties, including tensile strength and elongation at break.
- ISO 34-1 — Determines tear strength using specified test-piece geometries.
- ISO 48 series — Determines rubber hardness by specified hardness methods.
- ISO 188 — Evaluates accelerated ageing and heat resistance of vulcanized or thermoplastic rubber.
- ISO 815 series — Determines compression set after deformation under specified conditions.
- ISO 1817 — Evaluates the effect of liquids on vulcanized or thermoplastic rubber.
These standards are complementary rather than interchangeable. A rubber product may need tensile, hardness, tear, ageing, compression-set, and fluid-resistance testing before its performance can be fully assessed.
Who Should Use ISO 37?
- Rubber compounders and manufacturers controlling material strength and consistency.
- Automotive, aerospace, rail, construction, oil and gas, and industrial suppliers using rubber components.
- Manufacturers of seals, gaskets, hoses, belts, sheets, profiles, footwear, and moulded rubber parts.
- Testing laboratories responsible for mechanical-property testing.
- Buyers, procurement teams, and quality departments verifying material against specifications.
- third-party inspectors witnessing or reviewing tensile testing and batch acceptance.
How to Arrange an ISO 37 Inspection with TNV
- Share your requirement. Reach us by website, email, phone, or WhatsApp and tell us the product, rubber grade, lot size, location, specification, and whether you need sampling, witnessing, document review, or a complete inspection. We review the scope and send a clear proposal covering method, timeline, and cost.
- We plan the inspection. We confirm the applicable edition of ISO 37, test-piece type, sampling plan, conditioning requirements, acceptance limits, test location, equipment availability, and reporting format. Inspectors with suitable rubber or laboratory experience are assigned.
- We inspect and witness. Samples and specimens are identified and controlled. Where included in scope, our inspector witnesses specimen preparation and tensile testing, reviews equipment status, and records observations and results.
- We report. You receive a clear inspection report, reviewed internally for accuracy and delivered within the agreed timeframe.
- We follow up. We answer questions, clarify findings, and arrange follow-up or reinspection where required.
Why Choose TNV Inspection Division?
TNV Inspection Division is an independent, UAF accredited inspection body working under ISO/IEC 17020:2012. For rubber inspection, you get qualified personnel, defined sampling and reporting, impartial findings, and a clear connection between the measured result and the specification you need to satisfy.
We do not turn a tensile value into a vague promise. We show what was checked, how it was checked, which acceptance criteria applied, and what the evidence says.
Contact us
For professional, accredited, and globally recognized inspection services, Contact TNV Inspection Division today.
- Email: info@tnvib.com
- Website: www.tnvib.com
- Address: B-1/19/69 Sector K, Aliganj, Lucknow, UP 226024, India
Ensure quality, reliability, and confidence in rubber product inspection with TNV Inspection Division, your trusted ISO 17020-accredited inspection partner.
Frequently Asked Questions(FAQ)
Talk to TNV Inspection Division
Need an independent, accredited partner for rubber-product inspection and tensile-property verification against ISO 37? Contact TNV Inspection Division for a clear scope and a free quote.